1. Field of the Invention
This invention relates generally to pest control systems and methods therefor and, more particularly, to a system and a method for repelling pests using ultrasonic frequency sound.
2. Description of the Related Art
Efforts to control pests such as insects and rodents extend far backward in time. The desire to control pests stems from the irritation caused by such things as insect bites, to the problems of disease and destruction caused by larger or more aggressive pests such as rats. Most pest control solutions have addressed the problem by spraying toxic chemicals, or trapping the offender. Both of these types of solutions have their own attendant problems due to the requirement to dispose of the trapped or killed pest, a process that is at least unsightly and at worst risks the spread of disease. More sophisticated pest control solutions have addressed controlling pests through the use of devices that repel the pests. The most common of these devices broadcasts ultrasonic sounds at frequencies which irritate or impact the central nervous system of the pests. system of the pests. If sufficient irritation is present, the pests will leave the area of the ultrasonic sound broadcasts.
However, even the use of ultrasonic sound has its own drawbacks that must be addressed. For example, the broadcast of ultrasonic sound of constant duration, or even a semi-regular duration, can result in the pests becoming habituated to the ultrasonic sound much as a person who lives next to an airport or a train station can become habituated to that noise. When the pest habituates to the ultrasonic sound at that level they will cease to be repelled by the broadcast of the ultrasonic sound. An additional problem is that ultrasonic sound is highly directional and therefore its effects attenuate very rapidly with distance and direction. Currently available ultrasonic pest control devices are typically stand-alone devices containing a single ultrasonic transducer that points in one direction, with the result that these devices are only suitable for protecting a small area. Such devices are also typically of limited power, which further limits their effective broadcast area.
Most devices also use a single frequency transducer, and even though the advertised frequency range may be 30 kHz in width, the response curve of ultrasonic transducers is actually very sharp and only the center area of that 30 kHz frequency width is actually at the maximum advertised sound pressure level and therefore only that center frequency is maximally effective. The drop off in the sound pressure level for the frequencies that are off center result in a much less effective broadcast area. Other problems also exist in that the frequency range of the device must be carefully selected to not only target the specific pest, but also to avoid affecting household pets such as dogs, cats, birds etc. which, for example, are sensitive to the frequencies below 30 khz.
Therefore a need existed for a system and method that overcomes the directional and attenuation problems, thereby effectively covering a large area with the ultrasonic frequency broadcast. A further need existed for a system and method of using multiple transducers and high power output circuits to achieve large protected areas. A need also existed for a system and method of using multiple transducers with varied center frequencies to provide a broad effective frequency response curve. Yet a final need existed for a system and method of generating and broadcasting ultrasonic sound waves that will not affect household pets.